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VII. AREA OF OPERATION - NAVIGATION
Basic Navigation Goals; A. Task: PILOTAGE AND DEAD RECKONING; ...Common Navigation Faults ; ...Dead Reckoning;
...B. Task: NAVIGATION SYSTEMS AND RADAR SERVICES; ...C. Task:: DIVERSION;...D. Task: LOST PROCEDURES; ...Keeping it Simple; Compass; Compass Errors; Swing the Compass; A New Age; Magnetic Variation; ...VOR Magnetic Variation; Pressure Flying Long Distances; ...Selecting Altitude and Route; Isogonic Variation; ...Opinion with Humor; ...Method for Folding Charts; ...Local Conditions; ...The Last Word on Variation ... On Having Charts; ...
Basic Navigation Goals
The basics of navigation is to avoid obstacles and get to the destination with required reserves of fuel. Preciseness in navigation is required by the FARs and ATC to provide separation and tracking when assigned electronic headings and related altitudes.
PILOTAGE AND DEAD RECKONING
References AC 61-21, AC 61-23, AC 61-84
P 1. Knows application and distinction between pilotage and
P 2. Uses pilotage (landmarks and charts) to navigate plotted course line. Computes speed, times and ETA Compares with ETAs and fuel used.
P 3. Identifies landmarks by relating surface features to chart symbols.
P 4. Navigates by means of pre-computed headings, ground speeds and elapsed time.
P 5. Corrects for and records the differences between preflight fuel, ground speed, and heading calculations and those determined enroute.
P 6. Verifies the airplane's position within 3 nautical miles of the flight-planned route at all times. All courses maintained laterally + 3 miles.
P 7. Arrives at the en route checkpoints and destination ETAs + 5-minutes,
P 8. Maintains appropriate altitudes + 200' and headings + 15 degrees;
P 9. Completes appropriate checklists.
EX Plotting course, selecting checkpoints, computing data based on forecast data, how to establish course and stay on course, locating checkpoints, how to compute ground speed, ETA's, fuel use, correcting ETA's into arrival airports.
Destination and course to be within three nautical miles, altitude + 200 feet, arrival within +5 minutes, headings within + 15-degrees
Pilotage is flying a course line by charted reference to ground points. Dead reckoning is flying a route based upon course, time, and distance from a known point using estimated winds. Plotting the course begins with drawing the line on the sectional. Using a highliter pen or spaced multiple lines makes the course line easily discernible. Determine the True Course, determine the nearest variation (angle between the north and magnetic poles) and compute the Magnetic Course for entry on the course line. Since the Magnetic Course has no wind factor computed, it is a good reference for in flight wind correcting.
You are required to estimate a time of arrival (ETA) at a particular checkpoint. You are allowed + 5 minutes error in ETAs ATA, + 200' in altitude, + 10 degrees of heading, and + 3 nautical miles of course. If you cannot fly pilotage within half of these tolerances you will have difficulty passing the test. The examiner is allowed to create distractions to determine your ability to divide your attention.
Checkpoint selection is critical since a good checkpoint has three verifiable features, one of which may be a VOR radial. A day checkpoint may be invalid for night. There is some advantage in spacing checkpoints evenly from the destination. Keep points on the pilot's side as much as possible. Above 3000' don't use power lines or railroads. Lakes change during the year. Visibility conditions and altitude can greatly change the value of a checkpoint. Your skill in correlating a chart-symbol to the landmark seen from the airplane is essential.
The Compass Heading of the aircraft is the way the navigational computations say we should point the plane to allow for the wind, once we are established on course. Since these computations are based on forecasts they are at best estimates which must be adjusted in actual flight. The forecast winds are relative to True North in knots. We use the True Course line drawn on the sectional and True Air Speed in knots from the manual to compute the True Heading and Ground Speed. True heading is then corrected for variation and deviation to obtain Compass Heading, which is where the paragraph started. Fly to your first checkpoint and turn on course. Re-set your heading indicator and confirm your course. Sight on something as far ahead as you can see and start looking for your next checkpoint.
The computed Ground Speed is used to compute ETA's (estimated time of arrival) along the route. These times are in turn used to compute fuel consumption. Estimates of fuel consumption are based upon the manual the actual consumption at the end of the flight can be very educational indeed. The pilot who records fuel use on all flights gets insight into actual aircraft performance. Fly fuel use by time. Most aircraft are NOT topped off to full tanks because of fuel that may be wasted due to heat expansion.
Since wind conditions may vary the departure from an airport,
it is vital that the aircraft be established on course as soon
as possible. It is easily possible to depart incorrectly and
exceed the 3-mile course error before reaching 1000'. By telling
the tower that you plan to depart on course to your destination
you solve a multitude of problems. Fly directly to your first
checkpoint. Use the checkpoint CHECKLIST Carefully select a point
as far ahead on course as you can see and fly to it. If possible
reach your first checkpoint level at cruising altitude. This
makes possible a time check at the second checkpoint and computation
of an ETA. Destination ETA should be estimated at every checkpoint
based on checkpoint ATA. The planning technique that makes ETA
at destination very easy is to try to make your checkpoint distances
the same measuring backwards from your destination. The only
uneven distance should be from your departure to your first checkpoint.
See training material on use of checkpoint checklist.
1. Failing to use CHECKLIST for climb, leveling, checkpoints, and descent.
2. Failing to accelerate to cruise before fine trimming.
3. Being off course and not correcting.
4. Not setting Com/Nav radios ahead of time.
5. Holding head down while reading charts or using computer.
6. Failing to estimate heading required to correct wind and then flying that heading.
See instructional material related to cross country, checkpoints and radio.
The applicant must plan a cross-country to the maximum range of the airplane with required reserve. This is a test of judgment as well as computational accuracy. The major judgments involved are weather considerations, aircraft performance, airport requirements, navigational options, considered alternatives, and use of resources.
A method of navigation without the use of checkpoints predicated on direction, time, and estimates of speed and wind. Contrary to popular opinion, it has nothing to do with 'ded' as in deduction. As 15th century sailing ships began a voyage a rope with evenly spaced knots was tied to a log. The log was placed 'dead' in the water and the rope was played out over a fixed amount of time as the passage of knots was counted. The result of this gave a time over distance that was calculated as knots per hour and recorded in a logbook. Lindbergh used dead reckoning while flying the Atlantic. The accuracy of this method depends on several factors:
1. Selection of the initial heading based on wind correction
2. Estimation of ground speed based on true airspeed and wind effect.
3. Accurate timing.
NAVIGATION SYSTEMS AND RADAR SERVICES
REFERENCES: AC 61-21, AC 61-23, navigational manuals
P 1. Knows uses and limitations of navigational aids and radar
P 2. Selects, identifies and uses appropriate aids and radar services
P 3. Uses facilities to confirm aircraft location.
P 4. Intercepts and tracks a given radial or bearing, if appropriate
P 5. Recognized and describes the indication of station passage, if appropriate.
P 6. Recognizes signal loss and takes appropriate action.
p 7. Uses correct communication procedures and acknowledgments with ATC.
P 8. Flies + 200' at all times of appropriate altitude. Uses CHECKLISTS
EX Use NAV radio and ident code compared with sectional; centers OBS from/to; turns plane to course; checkscompass, heading indicator, OBS readings; limits wind correction to 30 degrees with ever decreasing corrections; does not chase needle at station passage; watches for red flag; uses CHECKLISTS. Within + 200 feet of altitude, locates aircraft position using radials, intercepts and tracks a given radial. Recognizes signal loss and takes appropriate action. Describes station passage.
The initial selection of a VOR station is dependent upon your location relative to the station, altitude, the distance and the terrain. 40 miles is the usual general aviation distance limit for accurate usability. Since line-of-sight is a limiting factor the distance may be much less because of the terrain. It is essential that every VOR signal be identified and confirmed with the sectional for its code. Lack of identification is the way to tell if the VOR is unusable. If a service man is making adjustments it may appear to work but accuracy is not assured without the IDENT. Once identified be sure to turn the IDENT volume down.
Part of the AIM, called the Airports/Facility Directory available at all FSS, lists the terrain/directional limitations of VOR's. The latest available should be purchased shortly before you plan to take the flight test from a local FBO. The Concord VOR is unusable in a wide arc toward Mt. Diablo. The signal may operate the needle, the IDENT work, and you can fly into the mountain. You must know the terrain in order to use a VOR safely. Using an out of date A/F D is a no-no. Centering the needle with the OBS requires some degree of dexterity. The weaker the signal the more the needle waves.
Behind terrain or at maximum line-of-sight ranges for a given altitude the waving may make the VOR unusable. If this is the case learn to recognize it. Hold the OBS knob between two fingers and move it back and forth in ever decreasing amounts until the needle is centered. Read the TO/FROM window to confirm setting and heading to turn aircraft to. Don't delay-turn immediately.
After turning aircraft to initial heading check compass, heading
indicator, and OBS for agreement. They must agree for you to
avoid reverse sensing that causes the needle to work backwards.
Any delay in turning the aircraft will cause the needle to swing
excessively. In any event, re-center the needle and fly the corresponding
heading. Watch the needle for movement caused by wind drift.
This movement can only be determined if ACCURATE headings are
flown. After a few minutes if the needle moves to one side, make
a heading correction 30 degrees or less designed to re-center
the needle keeping in mind a heading that will be required to
keep the needle centered. This is a guessing game similar to
finding a number between two other numbers on a computer. With
practice and some knowledge of the forecast winds you can become
quite accurate. The key to flying the VOR is the ability to fly
headings while distinguishing between actual and transient movements
of the needle.
Flying to a VOR is like flying into a 40-mile funnel. The closer you get to the station the more sensitive the needle becomes to 1 or 2 degree heading changes. Recognize that winds will change both with position and altitude. This means that the correction at one point will not necessarily apply further along. Be prepared to make heading adjustments as necessary, hopefully in ever decreasing amounts until one heading keeps the needle centered until station passage. Learn to recognize the rather rapid needle movement indicative of passage. Remember that the higher the crossing altitude the larger will be the cone of confusion. This means that the station passage heading must be held for periods of time, depending on altitude, before the needle will function properly on the other side of the VOR.
The VOR is frequently used as checkpoint backup indicator when map references may be limited. A VOR is selected that will give radials FROM at an angle 60 to 90 degrees to the course line. The closer to 90 the more accurate. Draw a line on the sectional from the VOR to the checkpoint. Find the VOR frequency, code, and OBS radial from and write them on a navigational log and on the sectional. As part of your checkpoint CHECKLIST you should have an item specifically for setting and re-setting your VOR.
A properly set OBS (FROM the VOR) for a checkpoint will cause the needle to start moving within 10 degrees of the radial. The needle will be on the side toward the VOR. As you proceed toward the checkpoint the needle will move closer toward the center. It will center at the radial set on the OBS and then move to the side away from the station. If the station is very close to the course line it is possible for this swing to occur so fast that it will not noticed. Be sure to observe the side the needle is on since this is the best clue as to the position of the checkpoint.
While it is necessary to demonstrate pilotage as the basic form of navigation, it is also expected that the pilot be able to perform using radio aids. Over dependence upon radio aids to navigation seems to be a common training error. The fact is that when weather and flight conditions are the poorest the practical use of the VOR decreases. The VOR range is a function of line of sight, which is in turn dependent upon altitude. If flight must proceed within 700/1200 feet of the surface due to ceilings the VOR range becomes less than 20 miles in level terrain and even less if terrain intervenes.
Flying to VOR's tends to put you in the major flyways with heavier traffic. Undue reliance on the VOR reduces pilotage skills and gives a false sense of navigational skill. Use the VOR only when it is honestly the best route since its limitations become greatest when you need them most.
See instructional material related to checkpoints.
REFERENCES: AC 61-21, AC 61-23
P 1. Knows the problems and solutions related to a diversion.
P 2. Selects an appropriate alternate airport and route.
P 3. diverts promptly toward the alternate airport.
P 4. Makes an accurate estimate of heading, ground speed, arrival time, and fuel consumption to the alternate airport.
P 5. Maintains the appropriate altitude, _200' and + 15 degrees
EX Factors of selection, present position, location of alternate, sectional use for distance and direction, altitude for visibility and insurance, communication procedures, decision making capability, division of attention, priorities. Arrival procedure are determined by communications. Accurate estimate to heading, ground speed figured, estimated time of arrival, fuel consumption, altitude -+ 200 feet and course held within + 15 degrees.
Reasons for diversion can be numerous such as a kidney stop, airsickness, weather, fuel, mechanical, turbulence, and precautionary. Every flight should be planned with the possibility of a diversion in mind. This flexibility should be part of the mental set as an antidote for get-there-itis. Along the route, possibly as part of your checkpoint CHECKLIST you should have noted diversionary airports and their radial from the nearest VOR. On the sectional write pattern altitudes, frequencies, and other pertinent data. KEEP YOUR CHECKLIST OUT.
If the pre-planning has been done correctly a number of the elements of this task are in place. First you will know where you are. Visually triangulate your position by using references to sides and front. This means that while flying up a valley covered with fog, with Mt. Diablo on your right and Grizzley Peak in the Oakland hills to your left, you should approximate your position as Walnut Creek. This skill can be developed with practice and conscious effort. Try to keep oriented along your route and have in mind the direction and location of airports. Practice locating private fields that may not be on the sectional. Keep an eye out for wind indicators and learn to relate what you see with the winds you find on the ground. Learn the terrain altitudes, power line locations, and obstructions so that you can make reasonable judgments as to emergency choices.
When required to divert, for whatever reason, turn immediately, maintain altitude as much as possible, fly the airspeed for best range. Use more power against the wind and less with the wind. Tell the examiner why you are doing this. Once headed in the selected direction start using the sectional to locate yourself and the emergency destination. Fold the sectional for your course line or make a line. Altitude is insurance. Use the plotter and VOR rose to determine course. Be sure to correct for variation if using plotter only. Fly estimated heading. Estimate time, distance and fuel. Keep attention divided.
Keep altitude until sure of arrival procedure. Set radios. Listen on COM while setting VOR radial for intercept. Maintain altitude until alternate is located. If contact is established an arrival can be planned, otherwise maintain altitude of at least twice pattern altitude. Use wind and runway indicators to determine arrival sequence.
Have the manual available but be familiar with the glide range to altitude ratio and short field performance of your plane. Know the effects of stopping the propeller on glide. Remember the first item in any emergency is CHECKLIST.
The element of judgment is more difficult to explain. Your choice of where to go and what to do may differ from that of the examiner. Don't try to second guess, make a considered decision and stay with it if possible. You would do well to explain the what and why of your actions. If task requires partial or no power be sure to trim for best glide. Don't let the wind blow you away from your field. There are far more corrective alternatives for being high than low. Keep your priorities in order. Fly the plane (airspeed), navigate (to arrive at a pattern altitude abeam numbers on downwind), and
then communicate (121.5 or advisory). Use your CHECKLIST. See instructional material on emergencies
REFERENCES: AC 61-21, AC 61-23
P 1. Exhibits knowledge of the flight elements related to
getting lost and getting found. Knows the psychology of being
lost is initially denial, then anger and finally acceptance.
P 2. Selects the best course of action when given a lost situation. Has an options list and makes safest selection. Uses CCCC if in doubt. Uses 'lost' checklist.
P 3. Maintains heading of aircraft. Climbs.
P 4. Identifies the nearest concentration of prominent landmarks. Seeks visual reference.
P 5. Uses navigation systems/facilities and/or contacts an ATC facility for assistance as appropriate. Gets airport information such as wind, runway, traffic, and pattern altitude.
P 6. Plans a precautionary landing if deteriorating weather and/or fuel exhaustion is imminent.
EX Being lost effects on thought processes, CHECKLIST meaning of 4 C's, using VOR radials, radar assistance, DF steer, limitations, effect of one additional problem such as weather, fuel, mechanical, or personal, airport Vs off airport landing. Maintains original heading, identifies nearest landmarks, uses navigational aids, contacts ATC for assistance, plans a precautionary landing if necessary.
The simulation of lost procedures is impossible, simply because of the mentally disabling effects of being lost. At best you must explain the use of the CHECKLIST. There is a difference between being misplaced and lost. The misplaced pilot is to one side or the other of course and still may be locating checkpoints and (incorrectly) accepting his position as O.K.
The lost pilot may be holding a course that is incorrect and causing an ever increasing deviation from the checkpoints. He may locate places and call them checkpoints or locations that are completely wrong. When identifying a place he shouldn't say, "That's Gotta' be..." because it doesn't. He may not even recognize that he is off course and misnaming locations. He is lost and doesn't even know it. Recognition takes place very gradually, sneaking into the consciousness and disabling the brain. The CHECKLIST is the best way to put things in order.
Habitual reliance on prominent checkpoints such as isolated mountains or lakes leads to a complacency easily shattered by 4-mile visibility. The distance between checkpoints should be related to aircraft performance and visibility. Your ability to recognize and correctly identify checkpoints and your relationship to them is the best preventative. If you know where you are you may have changed "lost' to "misplaced'. Once 'lost' is changed to 'misplaced', fly directly to your course. Intercept no later than the next checkpoint.
The placement of VOR's in conjunction with altitude and terrain may permit you to obtain a cross bearing of two radials. If this is the case, use standard procedures of frequency, identification, centering OBS on FROM. Transfer the VOR information to the sectional. By using two different VOR's at as near 90 degrees to each other as possible a very accurate position can be determined. It is important that in doing this procedure the attention be carefully divided in and out of the plane. Skill in getting two bearings with one VOR requires practice. Avoid having the aircraft cover too much distance, thus voiding the accuracy. If ceilings force you below 1000' this process most likely will not be available to you.
With good weather, adequate fuel, and a controlled aircraft being lost is not an emergency. Any one of the above, when added as a negative factor to being lost, creates an emergency. The 4 C's, (climb, communicate, confess, comply) makes possible the addition of ATC brains which are free of 'lost' disabilities. Climbing gives communications range,
Communication puts skilled ATC brains into the problem, confession relieves much of the pressure and presents others with the problem. Compliance with advice directs you toward the best solution. If ever you fly off the edge of a sectional the 4 C's is the preferred solution. One possible unpleasant side effect of being lost is that you may, unknowingly, be flying into a restricted area, ATA, TCA, game refuge, or worse. It is not uncommon to have such flights met by military aircraft and escorted down for interrogation, tracked by ATC for investigation, or held by police authorities once on the ground.
One major difficulty in locating an airport while lost is that while you see the airport you don't know where it is, its name, or requirements. Try to overfly in such a way as to avoid the possible pattern altitude. If it appears to have a tower, try the universal FSS frequency of 122.2. If you seem to be running out of options, try 121.5 or ground frequencies to get the tower frequency. If your situation is critical don't hesitate to use a military field. While technically no communications are required at an uncontrolled airport, some effort should be made. Use standard patterns and approaches as much as possible.
An off airport landing greatly increases the probability of aircraft damage or injury. However, if this becomes the only viable alternative do not hesitate. Plan the landing while visibility, weather, and fuel permit several efforts. Make low passes over the selected field to determine the best use of terrain and wind. Use your CHECKLIST and be sure to prepare the cockpit both for landing shock and escape. Make as near normal approach as possible. This usually means landing at lowest possible ground speed.
(1) I try to get my students to develop skills in getting all but the first distance between checkpoints all equal. Checkpoints are spaced closer together the poorer the visibility. Doing this essentially removes need for the E-6-B. Time between checkpoints allows you to determine ETA just by counting spaces. Points to begin descent and make radio contact are marked on the course line.
(2) Since winds are never as forecast, I use map course line as magnetic course and adjust heading required to get from checkpoint to checkpoint. ATIS is copied on hand for best availability. Anticipated entry and crosswind are diagramed on ATIS.
(3) We do all the figuring as in a normal log but transfer essential information to the sectional. Essentials include marking 90 degree line from course line to checkpoint. Left side is preferred over right and on course line is least preferred for checkpoints. Frequencies are put on chart along with airport information. As unexpected frequencies occur they are put on sectional. Frequencies trend to remain the same over the years. Times and fuel tank changes are entered directly to the sectional course line. FSS frequencies and contact points for opening and closing etc. are marked on sectional.
(4) Post-it's are layered according to projected flight. Used information is stuck under the active papers. Multiple pens and pencils are hung by linked chains of rubber bands in various places.
(5) Just as the preflight checklist is hung to a clip cord
about the neck so is the emergency list hung there once
(6) The sectional and an occasional post-it is all that is really required if things go as planned. When things don't go as planned additional material is kept beside the seat...never in back. When I have a student throw things in back, I throw them way back.
See instructional material on getting found and locating.
The magnetic compass depends on the horizontal component of the earths' magnetic field. The directional properties of the lodestone were known to early man. The term magnet comes from the name of a region in southern Europe which was a major source for lodestone. The development of the magnet grew form a floating needle in a straw, to the needle in a cork, a pivoted needle, the pivoted card, the pivoted card in a bowl, to the use of gimbals, and finally the liquid chamber with a pivoted card.
Compasses were in use as early as the 12th century but their operation was imperfect and not fully understood. About 18090 Mathew Flinders discovered a solution to the problem of local attraction. Deviation as used in aviation. Flinder's Bars, large masses of un-magnetized iron, are universally used on ships. In 1838 Sir G. B. Airy used magnets and iron to neutralize effects of iron ships.
The initial dry card compass was developed by Lord Kelvin who determined that a cards steadiness depended on the natural period of vibration of card and needle. A light card with a heavy rim was suspended by a pyramid of threads to a central pivot point. This produced a steady card. The use of a liquid float chamber with the buoyancy of the magnet and card only slightly less than weight to reduce fraction. The liquid has a dampening effect as well.
--The compass, unlike the GPS, does not have any built in
--You can make a compass fail, however, by making an extremely violent maneuver
--If there is a bubble in the fluid an extremely rapid descent will force all the fluid out and fail the compass.
--Runway numbers are rounded off to the nearer 'ten'. So runway/compass agreement may be off by five.
--You can find compass variation from true north by referencing the north arrow of the VOR compass rose.
--Every compass has a posted deviation card to show what to fly for a given compass heading.
--For planning purposes you figure in variation, deviation, and wind correction.
--For actual flying you fly the compass heading that will take you to a specific checkpoint.
--Suggest lining up the first two checkpoints to determine the compass heading required to keep alignment.
--You are combining dead reckoning, pilotage to fly your VFR route.
--With evenly spaced checkpoints you don't need to figure speed. Just figure ETA.
FAR 23.1327 Magnetic direction indicator.
(a) Except as provided in paragraph (b) of this section--
(1) Each magnetic direction indicator must be installed so that its accuracy is not excessively affected by the airplane's vibration or magnetic fields; and
(2) The compensated installation may not have a deviation in level flight, greater than ten degrees on any heading.
(b) A magnetic non-stabilized direction indicator may deviate more than ten degrees due to the operation of electrically powered systems such as electrically heated windshields if either a magnetic stabilized direction indicator, which does not have a deviation in level flight greater than ten degrees on any heading, or a gyroscopic direction indicator, is installed. Deviations of a magnetic non-stabilized direction indicator of more than 10 degrees must be placarded in accordance with Sec. 23.1547(e).
FAR 23.1547 Magnetic direction indicator.
(a) A placard meeting the requirements of this section must be installed on or near the magnetic direction indicator.
(b) The placard must show the calibration of the instrument in level flight with the engines operating.
(c) The placard must state whether the calibration was made with radio receivers on or off.
(d) Each calibration reading must be in terms of magnetic headings in not more than 30 degree increments.
(e) If a magnetic non-stabilized direction indicator can have a deviation of more than 10 degrees caused by the operation of electrical equipment, the placard must state which electrical loads, or combination of loads, would cause a deviation of more than 10 degrees when turned on.
The inverted Dixie cup model as the aircraft magnetic compass can be used in simulating a compass circle) containing a magnetic element. Put major directional markings on it and on the point of a pencil. The cup hangs straight down regardless of any forces applied. Now consider the cup in the presence of a magnetic field. The magnet in the "bottom" of the cup tries to align its magnetic axis. The center of mass is no longer directly below the pivot point. Any turning movement of the cup seems to come from the tilt that causes the center of mass to be offset from the force of gravity. This causes the compass reading be affected by any acceleration.
You'll have to go to an airport that has a compass rose. My A&P says you must use a mechanic to make adjustments.
You need a brass or plastic straight blade screwdriver. A new deviation card (available from any instrument shop)
Keep the engine and radios on. Have your helper help you to
get to the desired position. He
should be briefed as to the steps below.
Go to the compass rose and taxi up on it into the N heading, remove the old card and beneath it you'll see 2 small screws, one marked N-S & one E-W. Adjust the E-W to center N on the compass spin the plane to the E and adjust N-S to center it repeat with S then West and go around a couple of times until everything is as good as it will get. Now go do all the Cardinal points or degrees marked on the card and not the deviation on the deviation card. Now you have a swung compass and a fresh deviation card.
The N-S adjuster is used when the plane is pointing North or South, and the E-W adjuster when the plane is heading East or West. Start at N, and rotate 90 degrees (clockwise for the examples here) between each adjustment. Center on 360 deg., then center on 090 degrees, then halve the error when heading south, then halve the error when heading west. Continue with (at least) one more complete rotation, halving the error with the appropriate adjuster at each point.
Then, position the plane at every 30-degree heading on the compass rose, and note the compass card reading -- enter this reading on the deviation card.
We are now entering a new age of navigation. At the same time we are leaving behind a history of basic navigation skills. Point to point flying is so easy that only system monitoring is required. The failings of cross-country skills are still dominated by fuel problems, judgment decision deficiencies, old airplanes poorly maintained and deficiencies in basic flight techniques.
Here is how I diagram an explanation for magnetic variation. Take an 8 x 10 piece of paper.
1. Draw a circle as large as the paper will allow.
2. Draw a simple map of the U.S. Mark Chicago on your map.
3. Put the true north pole at the very top of your circle.
4. The magnetic north pole is about 1200 miles down a line from the north pole and Chicago. Make a guess and put an x to represent the magnetic pole. This pole is where your compass points. Forecast winds are traditionally given based upon the true north pole. Airport winds are magnetic based on the magnetic pole. This difference is why we must go through the flight training mathematics of changing from True Course, the line you draw on a sectional, to Magnetic course which is the way your compass reads that charted line.
5. Pick a spot to represent San Francisco on your map. Draw two lines to S.F., one from each of the poles. The angle at S.F. made by the two lines should be about 15 degrees. The line through Chicago and both poles is a "0" angle known as the agonic line.
Now pick a point on the map where you estimate your airport to be. Draw two lines again from the two poles. The better you have drawn your map and poles the more accurate will be the angle of difference between the two poles.
6. The dashed isogonic lines on the charts are to be used as approximation of the angle between the two poles
7. Isogonic lines change since the magnetic pole moves. This is the reason runway numbers change every few years. In the geological past the north and south pole have actually reversed several times.
8. Isogonic lines are titled in degrees East or West depending on their relationship with the agonic line through Chicago. An East variation is subtracted from true north to find magnetic north, a west variation is added.
This, along with the diagram is as simple as I can make it.
VOR Magnetic Variation
Q: Why is there a difference between the magnetic variation for the airport and the VOR located at the same airport?
A: According to the FAA's National Aeronautical Charting Office, when a navaid is first constructed, the antenna is physically oriented to true north. Then a potentiometer adjustment is made to slave the navaid with
magnetic north. This action matches the isogonic line, making it agree with a magnetic compass. Initially these two values are the same, but the magnetic variation of the Earth changes at a rate of 50.27 seconds of arc
per year. Navaids are commissioned and remain online 24 hours a day. Although periodic maintenance is performed as needed, reslaving the navaid to match the isogonic value requires a total shutdown, realignment, and a recertification flight check. Only when the navaid is out of tolerance by at least plus or minus 6 degrees will a reslaving procedure be initiated.
Flying Long Distances
It is possible for a pilot, knowing the pressure differential between departure and destination to fly a constant heading that will ignore wind drift throughout the flight. The distance will not be a straight line; rather it will be a shallow S for a longer distance that will take less flight time than will the straight line with applied correction.
When the destination pressure is higher than the departure the drift will be to the left. Pressure higher at the departure will cause any drift to be to the right. By determining a constant course for the entire distance we are able to ignore wind drift corrections and the associated decrease in airspeed. The proper constant heading will totally neutralize the wind effect.
Selecting Altitude and Route
--As a rule of thumb, true airspeeds maxes out at around 8000 ft. Fuel consumption is the same until that altitude, and then it starts dropping as you climb higher.
--Another rule of thumb is to keep the climb time to less than 10 mins for each hour of cruise. If your flight is 1 hr, keep the climb time to less than 10 mins, which translates to about 5000 ft AGL in a 172. The climb and descent taken together usually become insignificant compared with the effect of wind. Since the wind usually increases with altitude, the rule of thumb is to fly high with a tailwind and fly low with a headwind. But bear in mind that many pilots, and I'm certainly one of them, would gladly trade a few knots for smoother air. In still air all the way, speed/power, and therefore fuel economy (at full throttle), will improve by about 1% per 1000 ft of altitude.
Higher is better because:
1. It's easier to read a map if you're high.
2. You can glide further if your engine quits.
--During the summer the higher altitudes can make a considerable comfort difference.
--I've done spreadsheets with my aircraft performance factored for head/tail wind, and I can answer you the best power setting for maximum range given the predicted winds, and with climb power thrown into the equation, and the loss of airspeed in the climb configuration.
--The predicted winds are almost never as predicted. Within plus/minus twenty degrees of heading and plus/minus 5 to 10 knots of speed, but almost never spot on, so the spreadsheet is a SEWAG at best -- a recto random estimate as normal. However, if that climb to better winds cost me an extra gas stop, then what is that worth in time and gas to climb back to altitude? The equation gets pretty horrendous pretty quickly.
The answer is...bury your head in the charts for fifteen minutes, spend ten minutes with flight service on the phone, punch up a random number generator on the FBO's computer, get the nearest hemispherical altitude from the random number generator, nod your head sagely towards the airport bum's section of the pilot lounge and announce that "six-five looks like the best altitude today". To a person they will nod agreement and think, "That old Pete, he sure knows how to fly his airplane".
--A person who has experienced an in-flight fire (a statistically insignificant risk) will tell you to fly lower. All depends on perspective
--One of my biggest determining factors for shorter hops is the terrain
over which I am flying. Rough equals higher (5500 to 6500). Farmland equals
lower (3500 to 4500). I don't go lower than 3500 on a x/c unless ceilings make
I like to fly an airport vicinity route at AGL altitudes less than 3000'
I fly ifr (I follow roads) always on the right side. I always check for tall obstacles when driving and flying.
I like to depart with a takeoff turn that takes me over the airport on departure so I'm always on course.
I use radar advisories when my altitude permits.
I avoid VORs, aircraft corridors, airways, and common approach/departure routes to airports.
I always give my altitude when communicating.
In areas where I intend to fly at night I overfly daytime to find minimum altitudes and landing sites.
--From Seattle to Maine there are 45 degrees of variation difference.
--From San Diego to Key West there are less than 1lllll5 degrees of variation difference.
--The Agonic Line (Zero variation) cuts through Lake Michigan to the East shoreline of Florida.
--The eastern-third of the U.S. has more than 25 degrees of variation while the western two-thirds has a bit
more than 15.
--The East variation of the entire west coast has less than 10 degrees of variation while the western two-thirds has a bit more than 15.
--The East variation of the entire weslt coast has less than 10-degrees of variation with California having only slightly more than three of them for its entire length.
--The East coast has slightly more than l20 degrees variation from the tip of Florida to Maine.
--There are only ten degrees of variation difference from San Diego to New Orleans but twenty degreess from Seattle to Lake Superior.
--The lines of variation spread out over the U.S. much like a fan, getting further apart to the south.
--The northeastern pilot has more need for variation change awareness than anywhere else in the U.S.
--In the geological past there has been as least nine complete reversals of the the earth's magnetic fields.
--Runways are numbered to the nearer ten-degrees of magnetic direction. Runway numbers are in a constant state of flux (change) and cause confusion when using outdated runway information.
--All forecast winds are FROM a 'true' direction.,
--All runway numbers are magnetic as are all winds given at airports.
--Any line drawn on an aviation chart using lines of longitudes as a reference, will be a true direction.
The appropriate magnetic correction applicable to any plance on an aviation chart can be lbe obtained by using the numbers and letters including in the dashed magenta lines extending eldge to edge of the aviation charts.
--Often the airway going through a VOR will vary a degree or so on either side to correct for variation.
--An additional variation figure can be obtained through the use of the charted VOR compass rose's North index which is oriented magnetically.
--The true north pole exists at the top most point of all maps of the earth. The magnetic north pole exists
below the earth's surface as an ore body almost 1200 statute miles away from the true north pole.
--This underground situation is one factor in the 'magnetic dip' that occurs
with the compass when turning an aircraft.
--East variation exists when the compass used points east of true north. East Variation is always subtracted from true north to obtain magnetic direction. West variation exists when the compass used points west of true north. West variation is always added to true north to obtain magnetic direction.
--By drawing the angle from any point in the U.S. as a vertex to the true north pole and the magnetic north poloe located under the central islands of the Queen Elizabeth Islands you can approximate the variation by measuring the angle.
--The magnetic lines of force in the earth's magnetic field are not reallly straight or or slightly curved as shown on the charts. The actual lines are quite irregular and erratic and some areas ave charted warnings regarding magnetic irregularities.
--Since WWII the magnetic lines of force have been charted and re-charted in all oceans because the presence of submarines becomes apparent and revealed by noting changes in the charted lines. The Germans were aware of this and would 'hide' next to sunken ships in the shallow waters off Florida.
--On any flight over 300 nautical miles you should consider making 'legs using different variations.
--In California any southern course, true or magnetic will take you to the Pacific Ocean in less than two hours..
--In the New England part of the U.S. a true or magnetic course south will
take you to the Atlantic Ocean.
--In the New England part of the U.S. a true or magnetic course west will likely take you toward Texas and not California, Oregon or Washington..
Opinion With Humor
.The pilot knows where he is at all times. He knows this because he knows where he isn't. By subtracting where he is from where he isn't, he obtains a difference or course deviation. The pilot then uses course deviations to generate corrections that enable him to pilot his plane from a position where he is to a position where he isn't; arriving at the position where he wasn't and now is.
Consequently, the position where he is now is the position where he wasn't,
and it follows that the position where he was is the position where he isn't.
In the event that the position where he now is is not the position where he
wasn't, the pilots navigation computations have acquired a variation caused by
external factors. The variation is the difference between where the airplane
is and where the airplane wasn't. If the variation is considered to be a
significant factor , it too may be corrected for by use of a controlled
variable technique; however, the pilot must know where he was also.
The thought process is as follows; Because a variation has modified some of the information which the pilot has obtained, he is not sure where he is. However, he is sure where he isn't (within reason) and he knows where he was. The pilot now subtracts where he shouldn't be from where he wasn't and by differentiating this, then obtaining the algebraic difference between where he shouldn't be and where he was , he knows where he isn't.
The pilot is now able to obtain the difference between his course deviation
and his variation, which is called error. This allows the pilot to know where
he should be and where he wasn't; where he shouldn't be and where he was, thus
he knows where he isn't, the factor necessary to know where he is....."
Or you can just look it up on the GPS
Happy Flying R.Wallac
Method for Folding
You might want to try the following link.
It shows the method described below.
First, unfold the chart and lay it flat. Now, fold the chart the long way. In other words, fold it so it is still 3+ feet long, but only 10 or so inches high. Still with me? Now, starting at the left side, fold the chart along the creases in alternating directions. So, make the first fold "over", the next fold "under", etc. If anyone is still with me, your should now be able to open your chart to any location the same as you would open a book. This is great for east/west flights. Like I said, it means you only get one side of the chart...but if you buy two copies of the chart, then you always have one ready to go for the side you are on. And it is SO much easier to keep track of in flight.
Open an old sectional out until one flat sheet.
Suggest you run a sample marker line diagonally across the entire chart
Fold it into half lengthwise. Crease
Start at the left end and accordion fold all the way to the right side.
You can now use the folds like pages of a book to follow the line.
You never need more than two of the folds open at a time.
At the halfway point you flip the book over.
Try it, you'll like it.
To do a complete sectional you will need two of them. One for each side.
I wrote this little proggy to get the local conditions at my airport quickly. I thought some you might be interested in checking it out. It's a little rough but I thought if you guys are game, it would be
nice to have some feedback. It's free. No commercial aspirations....
The Last Word on Variation
I am about to purchase an electronic navigation computer which includes figuring in magnetic variation. The claim of accuracy is included in this device which means the use of 'known variation'. I have known of published errors of up to seven degrees.
My first question is that knowing that variation is undergoing constant change and periodically results in the re-numbering of runways, changes in charted isogonic lines on charts and magnetic north on compass roses.
Knowing this, where and how often can I find the routine used by (who ever
makes) the changes. I think that a compass rose charted change will differ in
time from a change in a runway number. I have no idea when isogonic lines are
Is there a programmed schedule? I know that my instrument approach charts give magnetic headings for runways that differ from the runway's magnetic numbers. Is there a way to determine the system used to sequence the changes? Where do I find out about what is going on?
NOAA provides an on-line calculator where you can enter a latitude / longitude / elevation and date and get the current magnetic declination. This would provide you with the best estimate of the declination (generally accurate to about 1 degree at ground level - more so under ideal solar conditions at aircraft altitude). The web site is at: http://www.ngdc.noaa.gov/seg/geomag/magfield.shtml
The "Field Value" calculator allows input of altitude, the
"Declination" is a simple D-at-the-surface-only calculator. The model
which these calculations are based on is updated every 5 years. We distribute
the model to NATO, NOAA, DOD, the FAA, and post online for others to access.
Unfortunately, providing a model with built-in expiration of 5 years in the future, does not ensure that the current models available will be used. They are the "IGRF10" and the WMM, both released in December of 2005 and valid through December 2009.
Why Variation is Inexact
The charted variation of VORs are on a Government Cycle just as are runways. Every few years you may have noticed that some of your local runways have a number change due to changes in the earth's magnetic fields. The same charted changes will occur in the location of isogonic lines on charts and in the magnetic compass roses around VORs.
You can learn more than you ever wanted to know at the following site. Ask
Susan your question, I did.
On Having Charts
The only FAA/FAR requirements that pertain to charts are:
Title 14 CFR section 91.503 (Large and Turbojet powered aircraft)
Title 14 CFR section 135.83 (Air Carriers-Little Airplane)
Title 14 CFR section 121.549 (Air Carrier-Big Airplanes)
The FAA has rendered interpretations that have stated the foregoing. The subject of current charts was thoroughly covered in an article in the FAA's July/August 1997 issue of FAA Aviation News. That article was cleared through the FAA's Chief Counsel's office. In that article
the FAA stated the following:
1. "You can carry old charts in your aircraft" "It is not FAA policy to violate anyone for having outdated charts in the aircraft"
2. "Not all pilots are required to carry a chart" "91.503..requires the pilot in command of large and multiengine airplanes to have charts". "Other operating sections of the FAR such as Part 121 and
Part 135 operations have similar requirements".
3. "since some pilots thought they could be violated for having outdated or no charts on board during a flight, we need to clarify an important issue. As we have said, it is NOT FAA policy to initiate enforcement action against a pilot for having an old chart on board or no chart on board". That's because there is no regulation on the issue.
4. "the issue of current chart data bases in handheld GPS receivers is a non-issue because the units are neither approved by the FAA or required for flight." "Nor do panel-mounted VFR-only GPS receivers have to have a current data base because, like handheld GPS receivers, the pilot is responsible for pilotage under VFR
5. "If a pilot is involved in an enforcement investigation and there is evidence that the use of an out-of-date chart, no chart, or an out-of-date database contributed to the condition that brought on the enforcement investigation, then that information could be used in any enforcement action that might be taken"
If you, as an FAA Safety Inspector, Designated Pilot Examiner, Flight Instructor, or other aviation professional are telling pilots something other than the foregoing then you are incorrect.
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